Bituminous road surface



Patented Dec. 1, 1931 UNITED STATES PATENT OFFICE.

1'1ELRJ EATN'N FBITSCH, OF SWINEMUNDE, GERMANY, ASSIGNOB TO MESSRS. FOX, STOCK- WELL & COMPANY, OF LONDON, ENGLAND BITUMINOUS ROAD SUB-FACE N0 Drawing. Application filed October 30, 1929, Serial No.

This invention relates toa process for building bituminous street surfaces, poor of interstices and of an equal compactness from top to bottom, using stone material of gradu ated sizes, the bituminous treatment made in a cold process.

It is known, to bring stone material, aggregate and chips of uniform particle size to the foundation of a street, and to consolidate and to sprinkle it with tar or asphalt in the hot or'cold process. For sealing the surface the top layer receives the known surface treatment.

These kinds of top layers .(tar-grouted or bituminous grouted) have the drawback that owing to'the missing of fine filling material numerous interstices remain in the top layer, and therefore the solidness and durability is greatly decreased, so that a large part of the binding substance sprinkled on the top layer runs through the interstices to the foundation, and the outer parts of the aggregate and chips are covered quite insufficiently by the binding substance, and in rainy weather these top layers, when treated in the hot process, remain for months, and when treated in the cold process, remain for weeks uncompleted and interrupt the t 'aiiic, till it is again dry weather. These top layers have also the disadvantage, that only the surface is sealed, that they lose of their compactne'ss gradually to the bottom, therefore they have not sufficient compactness to resist the demands of the traflic for a longer period. This important drawback is not only caused by the insufficient filling of the binding substance, but also that the stone skeleton is not composed and consolidated according to the principle of a minimum of interstices, e. g., the mixture of the used stone material and the ar 'angement of the single chip and aggregate layers not made to procure a minimum of interstices.

Inthe process according to this application, in which all the used materials in an efficient mixture and arrangement in layers are covered in the cold process on the building site with a binding substance, preferably with asphalt or tar emulsions or with efliciently prepared cold fluid tars or efiiciently 403,666, and in Germany October 6, 1928.

prepared cold fluid asohalts and consolidated by one rolling down, these disadvantages will not appear, and therefore absolutely compact street surfaces with a minimum of interstices can be built also in unfavourable weather. Hitherto this could only be made in the hot process, and not even in a suflicient way and only in dry and warm weather, whereas the use of the tar macadam and "-ai' concrete when the stone material must be covered in a hot condition with tar and brought to the building site in a cold condition and built in, has the large disadvantage, that the material during the transport and at the building site gets dirty and loses in its binding ability. The transport of the stone material and of the binding substance to a central point, where they are mixed, and the re-transport to the building site cause double loading and freight expenses, so that this process raises the price considerably. These top layers have also too many interstices, as the selection of the graduated sizes of the stone material, their mixture and arrangement in layers and the consolidation are not made according to the standard of this application, which is neces sary to avoid the prejudicial interstices as much as possible. These road surfaces, coust'ructed according to this application will never wave or corrugate orget slippery, in hot weather they will never soften or bleed, contrary to the top layers, produced in the hot process, which show very often these disadvantages. This'new kind of road surfaces can be made in three different methods, for instance Ewumplc I. 6-10 cm. thick. ngredients Millimeter: Granite chips (aggregate) or furnace-cinder 30-55 Coarse granite chips or i'urnace-cindcipsfl. 15-30 Asphalt or tar emulsion (-60% dry contents) or efficiently prepared cold fluids tars or efficiently prepared cold fluid asphalts.

7 vOn the old or new 7 10,

impregnation during the mixing.

can be moulded, as

Ewample III. as cm. thick. lngredie ts Millimeters Coarse granite chips or furnace-cinder 30 Medium granite chips 81Q Smudge or sand Sand Asphalt or tar emulsion (-60% dry contents) or efficiently prepared cold fluid tars or efiiciently prepared cold, fluid asphalts.

The road surfaces are made in two diiferent layers as follows:

face, which must at firstbe levelled down and profiled, the coarse binding layer is brought up, and impregnated with one ofthe above mentioned 'cold binding substances, either by hand on a mixing board, or by machine. A,

second fine filling layer is at once and according to the profile put on thislower binding layer, impregnated as the binding layer. WVh en using emulsions, they are broken after the mixture with the stonematerial and the impregnation, i. e. the decay'has taken place,

. the precipitated particles of tar or asphalt 1 have causeda close lutation of the stone and cinder ingredients; When using cold fluid tars' or cold fluid bitumina' the miXi-ngand process also takes place at once The mineral layers, impregnated in this way, are still ductile and the bitumina or tars do not congeal at once, but are flexible. NOW

- the top layer is c'o'nsolidated with a street and then the top roller of medium weight. As the mixture of the'graduated sizes of the stones and the:

arrangementof the layers has been chosen to attain a minimum of interstices, the fine filling layer is pressed into the lower binding 1 yer by the consolidation, so that parts of the top layer penetrate to the foundation and "remove nearly completely all interstices.

Preferably the accordingly mixed and arranged impregnated stone material is. pressed into each otherthrough a single rolling in the above mentioned way, If first the lower, layer would be rolled, as done hitherto, the

7 I t-hefine stone material of the top layer couldnot penetrate into the lower and fill the still existing inter; sticesi I Hereafter or after about a fortnight the top layer, which is consolidated in the meantime,

receives a slight surface treatment with impregn ated fine chips or sand to seal the small pores of the surface,should there be any.

- a mixtureof relatively [What I claim is: r

'1. The process for the construction and paving of roads which comprises-applying to a suitable foundation a layer consisting in coarse and relatively finer aggregate coated with bituminous composition fluid in the cold thereon a plurality of layers of mixedaggregate coated with bituminous composition fluid in the cold, the'aggr'egate of each of said 10' u macadam or pawl S a suitable foundation after the used stone is well mixed thereon a plurality of layers of lower layer would be already hard and lutated, so that name to this specification.

and superimposing v;

layers having a greater average degree of subdivision than the layer on which it is superimposed and each of the several layers consisting of particles of different sizes in proportions adapted to yield a mixture having a minimum of voids and thereafter rolling the whole.

2.7 The process for paving of roads which the construction and comprises applying to a layer consisting in a mixture of relatively coarse and relatively finer aggregate coated with bituminous emulsion and superimposing thereon a plurality of layers of mixedaggregate coated with bituminous emulsion fluid in the cold, the aggregate of each of said layers having a greater average degree "of subdivision. than the layer on which it is superimposed and each of theseveral layers consisting of particles of difi'erent sizes in proportions adapted to yield a mixture having a minimum of voids and thereafter rolling the whole.

3. The process for the construction and paving of roads which comprises applying to a suitable foundation a layer consisting in a mixtureof relatively coarse and relatively finer aggregate coated with bituminous composition fluid in the cold and superimposing mixed aggregate freshlycoated at the place of usewith bituminouscomposition fluidrin the cold, the aggregate of each of said layers" havinga greater average degree of subdivision than the layeron which'it is superimposedand each'of the several layers consisting of particles of different sizes in proportionsadapted to yield a mixture having a minimum of voids and thereafter rolling the Whole.

4. The process for the construction and paving of. roads which comprises applying to a suitable foundation a-layer consisting in a mixture. of relatively coarse and relatively finer aggregate coated with bituminous emulsion and superimposing thereon a plurality of layers of mixed aggregate freshly coated V voids and thereafter. rolling the whole;

In testimony: whereof I have signed my HERMANN riirrson. c 

